1. Field of the Invention
The present invention relates to a mobile station, a base station, a mobile communication system, and a communication control method where communications are carried out in the form of uplink reservation-based packet access.
2. Description of the Related Art
In the 3rd generation (3G) mobile communication system, data communications are carried out in the form of circuit switching. In the 3G system, random access is defined which has some similarities to reservation-based access in operations (for example, Non-Patent Reference 1).
Specifically, when a request for data transmission is generated in a mobile station, the mobile station notifies a base station of the request for data transmission by means of a Preamble. A Preamble is a form of reservation control signal for notifying the base station of a request for data transmission. The following data packet is fixed in length.
Under random access in the 3G system, when transmission data is long compared to the length of a data packet, for example, Preambles are frequently transmitted, because the size of data which can be transmitted at every random access is predetermined. As a result, it presents a problem that overhead and delay may increase. In order to handle this problem in the 3G system, a dedicated data channel is used. However, it presents a problem that delay for configuring the dedicated data channel may occur. Further, it presents a problem that channel resources may be occupied for a certain amount of time, even if transmission data does not exist.
When transmission data is short compared to the length of a data packet, the 3G system is inefficient, because wasteful transmission may occur.
In the future, reservation-based packet access will be necessary which supports various data sizes and requests for QoS, and a method of efficiently transmitting a reservation control signal under this reservation-based packet access will be a matter of concern.
[Non-Patent Reference 1] 3GPP TS25.211, 25.214